Approaches to converting sunlight to electricity using photovoltaic cells are primarily of two types: those that use flat panels of photovoltaic cells mounted in fixed orientations, and those that use tracking optical elements to concentrate sunlight onto smaller areas of photovoltaic cells. The latter type potentially affords higher power densities and lower equipment costs by reducing the quantities of photovoltaic materials required, thereby enabling the economic use of high-efficiency photovoltaic cells, whose cost in non-concentrating panels would be prohibitive. For example, triple junction photovoltaic cells employing type III-V semiconductors have recently demonstrated sunlight-to-electricity conversion efficiencies of greater than 40 percent, but the cost-effective terrestrial applications of such cells typically require their use at concentrations of greater than one hundred suns.
To date, concentrating photovoltaic applications have been largely limited to industrial-scale operations. Although a number of recently-developed concentrating systems use optical elements of relatively small size and are described as having a low profile, they remain poorly suited for the single largest sector of the market for products that convert sunlight to electricity—the rooftop panel market.
Most rooftop solar panel installations mount the panels in fixed orientations, where they have a low profile and unobtrusive appearance. A solar collector that combined the superior economics of concentrating high-efficiency photovoltaics with the ease of installation and maintenance, and aesthetics of conventional solar panels would provide unprecedented value to the owner and user. The requirement that a concentrating solar collector using tracking optical elements have a fixed shape with a thin profile like a conventional panel necessitates the use of many such optical elements mounted within a fixed base structure.
Proposed systems incorporating arrays of optical elements in arrangements contained within relatively thin fixed slabs mechanically link the elements to an adjustment mechanism shared by multiple elements. Such approaches have several drawbacks including that failures in the mechanical linkages between elements can cause tracking failures of multiple elements, that the mechanical linkages introduce a source of tracking errors due to imprecisions in the mechanism, and that servicing individual elements is complicated by having to manipulate mechanical connections.
Objectives of the present invention include providing methods of creating solar energy collection systems that:                Make economical the manufacture of concentrating elements of sufficiently small dimensions that arrays of such can be configured in panel-like enclosures.        Provide exceptional sun tracking accuracy, allowing the maximization of the concentration ratio and thereby minimizing the quantity of photovoltaic material required.        Maximize the aperture efficiency of the concentrating optical system by minimizing losses of light to spaces between the array elements.        Provide exceptional operational robustness and allow easy maintenance and servicing by making the removal and re-installation of elements simple and straightforward.        